7 Expressions [expr]

The comma operator groups left-to-right.

expression:
	assignment-expression
	expression , assignment-expression

A pair of expressions separated by a comma is evaluated left-to-right; the left expression is a discarded-value expression.

Every value computation and side effect associated with the left expression is sequenced before every value computation and side effect associated with the right expression.

The type and value of the result are the type and value of the right operand; the result is of the same value category as its right operand, and is a bit-field if its right operand is a bit-field.

If the right operand is a temporary expression ([class.temporary]), the result is a temporary expression.

In contexts where comma is given a special meaning, the comma operator as described in this subclause can appear only in parentheses.

f(a, (t=3, t+2), c);